Functional activity of the rat olfactory bulb related to different durations of odor exposure

We have studied the effects of different odor exposure durationson the functional activity of the rat olfactory bulb by usingthe 2-deoxyglucose (2-DG) method. This technique brings outodor-specific patterns of labeling in the glomerular layer ofthe bulb. In a first set of experiments, rats designated ascontrols were submitted to two stimulation conditions with cyclohexanonefor 40 min following 2-DG injection: group C-5—alternatestimulation (5 min odor–5 mm pure air); group C-20—continuousstimulation (20 mm odor-20 min pure air). In a second set ofexperiments, rats designated as ‘adapted’ were exposedfor 3 h to cyclohexanone before the 2-DG injection; then, threeconditions of stimulation were tested with the same odor duringthe post-injection period; group Adap-5—alternate stimulation;group Adap-20—continuous stimulation; group Adap-0—stimulationwith pure air only. In the two control groups, the total numbersof labeled glomerular foci were similar; however, group C-20showed a significant increase in the number of ‘heavily’labeled foci. This result suggests that under conditions of20 min continuous odor exposure, receptor cells do not adaptrapidly and totally. Results from the adapted groups showedthat only the group Adap-20 presented significant changes infunctional bulbar activity. An important decrease in the totalnumber of labeled glomerular foci and an absence of ‘heavily’labeled foci were noted in all rats of this group; their patternsof 2-DG uptake were greatly reduced in both complexity and contrast.These results highlight the importance of olfactory receptoradaptation under conditions of long-duration odor exposure.Fast recovery of receptor sensitivity when the stimulation isinterrupted is also suggested.     

Experimental warming disrupts reproduction and dung burial by a ball‐rolling dung beetle

1. Insects are sensitive to climate change. Consequently, insect‐mediated ecosystem functions and services may be altered by changing climates. 2. Dung beetles provide multiple services by burying manure. Using climate‐controlled chambers, the effects of warming on dung burial and reproduction by the dung beetle Sisyphus rubrus Paschalidis, 1974 were investigated. Sisyphus rubrus break up dung by forming and rolling away balls of manure for burial and egg deposition. 3. To simulate warming in the chambers, 0, 2 or 4 °C offsets were added to field‐recorded, diurnally fluctuating temperatures. We measured dung ball production and burial, egg laying, survival and residence times of beetles. 4. Temperature did not affect the size or number of dung balls produced; however warming reduced dung ball burial by S. rubrus. Because buried balls were more likely to contain eggs, warming could reduce egg laying via a reduction in ball burial. Warming reduced the humidity inside the chambers, and a positive relationship was found between the number of dung balls produced and humidity in two temperature treatments. Temperature did not affect survival, or whether or not a beetle left a chamber. Beetles that did leave the chambers took longer to do so in the warmest treatment. 5. This study demonstrates that climate warming could reduce reproduction and dung burial by S. rubrus, and is an important first step to understanding warming effects on burial services. Future studies should assess warming effects in field situations, both on individual dung beetle species and on aggregate dung burial services.     

On the mechanism of a high-frequency force generator in outer hair cells isolated from the guinea pig cochlea

Isolated mammalian outer hair cells elongate or shorten respectively by several micrometres when electrically hyperpolarized or depolarized. The experiments in this paper were designed to locate the force-generating mechanism that drives length changes in outer hair cells, and to determine some of its basic properties. The whole-cell mode of the patch-clamp technique was used to stimulate cells electrically and to perfuse them with specific drugs. The pattern of displacement of cellular organelles, and the relative displacements of the cell base and apex during electrical stimulation with the cell mechanically anchored at various points along its length, suggest that the force-generating mechanism is distributed throughout the length of the cell. Further experiments altering the shape, volume and intracellular pressure of outer hair cells suggest that the mechanism is closely associated with the plasma membrane. These experiments also demonstrate that the characteristic tubular shape of outer hair cells is maintained by membrane-associated structures with elastic properties that enable the cell to return to its original shape after deformation. The mechanism controlling length changes may, therefore, be composed of two elements in parallel, namely a force generating element and a passive elastic element. Inhibitors of ATP synthesis, or the presence of the non-hydrolysable ATP analogue AMP.PNP, perfused into outer hair cells, failed to inhibit length changes. Drugs against actin, including phalloidin, cytochalasin B and cytochalasin D, and against tubulin, including colchicine, nocodazole and colcemid, also failed to inhibit length changes. We conclude that the force-generating mechanism is, therefore, unlike most other forms of cell motility, and possible alternative hypotheses are briefly discussed.     

Predictability of food supply,but not ration,increases exploratory behaviour in zebrafish Danio rerio

Individual zebrafish Danio rerio were assayed for exploratory tendency in a serial open field test before and after being maintained on one of four diet treatments that differed in ration and in predictability of food delivery. Danio rerio became more exploratory after being maintained on a diet with a predictable delivery schedule. There was no effect of ration. Thus, exploratory behaviour is inducible by environmental influences independent of genetic predisposition or social interactions. These results have implications for management of correlated behavioural syndromes of exploratory and boldness of animals reared in captivity for later release into wild populations.     

Heat resistance of Cronobacter species (Enterobacter sakazakii) in milk and special feeding formula

Aim:  To determine D - and z -values of Cronobacter species ( Enterobacter sakazakii ) in different reconstituted milk and special feeding formula and the effect of reconstitution of powdered milk and special feeding formula with hot water on the survival of the micro-organism.
Methods and Results:  Five Cronobacter species (four C. sakazakii isolates and C. muytjensii ) were heated in reconstituted milk or feeding formula pre-equilibrated at 52–58°C for various times or mixed with powdered milk or feeding formula prior to reconstitution with water at 60–100°C. The D -values of Cronobacter at 52–58°C were significantly higher in whole milk (22·10–0·68 min) than in low fat (15·87–0·62 min) or skim milk (15·30–0·51 min) and significantly higher in lactose-free formula (19·57–0·66 min) than in soy protein formula (17·22–0·63 min). The z -values of Cronobacter in reconstituted milk or feeding formula ranged from 4·01°C to 4·39°C. Water heated to ≥70°C and added to powdered milk and formula resulted in a > 4 log₁₀ reduction of Cronobacter .
Conclusions:  The heat resistance of Cronobacter should not allow the survival of the pathogen during normal pasteurization treatment. The use of hot water (≥70°C) during reconstitution appears to be an effective means to reduce the risk of Cronobacter in these products.
Significance and Impact of the Study:  This study supports existing data available to regulatory agencies and milk producers that recommended heat treatments are sufficient to substantially reduce risk from Cronobacter which may be present in these products.     

The structure of the carboxyltransferase component of acetyl-coA carboxylase reveals a zinc-binding motif unique to the bacterial enzyme

Acetyl-coA carboxylase (ACC) is a central metabolic enzyme that catalyzes the committed step in fatty acid biosynthesis: biotin-dependent conversion of acetyl-coA to malonyl-coA. The bacterial carboxyltransferase (CT) subunit of ACC is a target for the design of novel therapeutics that combat severe, hospital-acquired infections resistant to the established classes of frontline antimicrobials. Here, we present the structures of the bacterial CT subunits from two prevalent nosocomial pathogens, Staphylococcus aureus and Escherichia coli, at a resolution of 2.0 and 3.0 A, respectively. Both structures reveal a small, independent zinc-binding domain that lacks a complement in the primary sequence or structure of the eukaryotic homologue.     

Elimination of Escherichia coli O157:H7 from Fermented Dry Sausages at an Organoleptically Acceptable Level of Microencapsulated Allyl Isothiocyanate

Four sausage batters (17.59% beef, 60.67% pork, and 17.59% pork fat) were inoculated with two commercial starter culture organisms (>7 log₁₀ CFU/g Pediococcus pentosaceus and 6 log₁₀ CFU/g Staphylococcus carnosus) and a five-strain cocktail of nonpathogenic variants of Escherichia coli O157:H7 to yield 6 to 7 log₁₀ CFU/g. Microencapsulated allyl isothiocyanate (AIT) was added to three batters at 500, 750, or 1,000 ppm to determine its antimicrobial effects. For sensory analysis, separate batches with starter cultures and 0, 500, or 750 ppm microencapsulated AIT were produced. Sausages were fermented at ≤26°C and 88% relative humidity (RH) for 72 h. Subsequently sausages were dried at 75% RH and 13°C for at least 25 days. The water activity (a_w), pH, and levels of starter cultures, E. coli O157:H7, and total bacteria were monitored during fermentation and drying. All sausages showed changes in the initial pH from 5.57 to 4.89 and in a_w from 0.96 to 0.89 by the end of fermentation and drying, respectively. Starter culture numbers were reduced during sausage maturation, but there was no effect of AIT on meat pH reduction. E. coli O157:H7 was reduced by 6.5 log₁₀ CFU/g in sausages containing 750 and 1,000 ppm AIT after 21 and 16 days of processing, respectively. E. coli O157:H7 numbers were reduced by 4.75 log₁₀ CFU/g after 28 days of processing in treatments with 500 ppm AIT, and the organism was not recovered from this treatment beyond 40 days. During sensory evaluation, sausages containing 500 ppm AIT were considered acceptable although slightly spicy by panelists.     

Effect of kosmotropicity of ionic liquids on the enzyme stability in aqueous solutions

This paper examined the effect of several pyridinium and imidazolium-based ionic liquids (ILs) on the protease stability in aqueous solutions. In general, the enzyme was found quite active at low concentrations of hydrophilic ILs. In aqueous environment, the enzyme was stabilized by the kosmotropic anions (such as CF3COO- and CH3COO-) and chaotropic cations (such as [BuPy]+ and [EMIM]+), but was destabilized by chaotropic anions (such as tosylate and BF4-) and kosmotropic cations (such as [BMIM]+).